Wednesday, December 26, 2012

Yeti Arrives at Mt. Erebus

After a frustrating 5-week delay, Yeti has finally arrived at LEH.  Due to a series of very unfortunate events, he's been stagnant at various locations since his "arrive-by date" of November 22nd.  Just this last week he's spent on the helicopter pad at McMurdo Station, waiting for weather to clear.  Since the only way to get up the volcano is by helicopter, we are completely at the behest of weather.  For some reason, it seems that the conditions are always opposite at LEH and McMurdo.  Most of the time, the weather up on the volcano is beautiful and clear, and we are above the clouds, and McMurdo is "hot," cloudy and snowy.  We rarely get any snow up here. 

It seems so long ago that Jim and I packed up Yeti in his box.  He is really easy to helicopter in, because he's exactly square, and can be slung by a helicopter.  Below is Yeti's arrival this morning.

This was our first helicopter in over a week, and we were also very happy to get butter and some "freshies."  We also said a sad goodbye to our UNAVCO friend Marianne Okal, who was doing some LiDAR of the crater and surrounding areas.

First look at Yeti in more than a month!  We asked the helicopter to drop the sling near the "RAC tent," or rapid-assembly-something tent, which ended up being the science staging area.

Yeti's first steps on Mt. Erebus, his flag blowing nobly in the 20 knot winds. 

Today Drea and I will go to Warren Cave to set up a tent so we can watch Yeti surveying from relative comfort, and so the laptop will continue to function.  Yeti's first survey will be around LEH to get him warmed up, then to Warren cave, for which we also have LiDAR data. 

Wednesday, December 19, 2012

LiDAR at Mt. Erebus

Today we said goodbye to Kevin Mickus (gravity man) and Jed Freschette (LiDAR man), two of our awesome team doing awesome science at Mt. Erebus.  In my previous post I described Kevin's gravity work, and here I'll describe Jed's LiDAR work, which ties into my ground penetrating radar surveys. 

LiDAR stands for Light Detection And Ranging, meaning it detects light (laser light, specifically) and also computes the distance the light has traveled.  A laser is shined at an object, which reflects and back-scatters that light, which is then received and analyzed by the LiDAR unit. Lasers are used because they produce a very narrow, intense beam of light, from which a reflected signal can be accurately associated with a specific point on the object of interest.  Therefore, LiDAR can obtain very fine resolution.

There are several types of LiDAR with different applications:
  1. terrestrial (urban, forrestry, etc)
  2. airborne (down-looking from airplanes, helicopters,
  3. space-borne - nir
  4. atmospheric (maps column of air space above) - green
  5. mobile
LiDAR is a popular tool for use in the cryosphere, because the landscape offers little contrast for traditional imaging methods.

Here on Mt. Erebus, scientists Jed Freschette and Drea Killingsworth are using LiDAR to map the accessible rooms of ice caves formed by the volcano.  This not only gives location, and extent of the caves, but an idea of volume and structure as well.  

LiDAR unit upon a tripod, with a target and tripod in the background.  Each scan round must have a GPS location, or be co-located to a dataset with location information.

LiDAR in the process of scanning the ice cave with green laser.  The swath of light is made by a rapidly scanning laser, and moves through a 270 degree field-of-view.

Sunday, December 16, 2012

Measuring Gravity at Mt. Erebus

Measuring gravity changes at Mt. Erebus will help measure the "plumbing" of the volcano or, how the magma flows within the volcano.  Our gravity man, Kevin Mickus, uses a gravimeter to measure local gravitational fields at many points around Mt. Erebus.

Gravity Principles

Though it's often drilled into our head during Physics I,II,III etc that the acceleration of gravity on Earth is 9.81 m/s^2, gravity at specific points on the earth changes due to various parameters.  Gravity changes with elevation, latitude, earth tides of the crust from the moon, and air pressure, to name a few.  In addition, the density of an object affects its gravitational acceleration and direction. 

Here at Mt. Erebus, gravity caused by the Earth is greater because we are at a pole rather than the equator.  Reasons for this include the "equatorial bulge," and the increased inertia caused by Earth's rotation.  The "bulge" results in a greater distance between and object and the Earth's center as compared to at a Pole, and therefore that object experiences a weaker gravitational pull.  The same rationale is applied to gravity at high altitudes.  The effect of altitude can be quantified by the following equation:

For studies of Mt. Erebus (we are currently at 11,500 ft. above sea level), we want to remove all these effects in order to obtain gravitational anomalies related to different densities of the volcano rock.  Denser material causes higher local gravitational fields, whereas the opposite is true of less dense material.  The two material extremes on any volcano are dense rock and less-dense magma.  Measuring gravity at Mt. Erebus can help locate where magma chambers exist.  Higher gravity measurements mean dense, cool volcanic rock, whereas lower gravity measurements mean less dense, hot magma.  The differences in gravity between these two extremes are very small.

The location and flow of magma reservoirs within a volcano are key to understanding its dynamics, including magma "plumbing system," volcano deformation, temperature distribution, and eruption mechanisms. 

Measuring Gravity

Gravity anomalies are measured with a gravimeter, and measured in milligals.  A Gal is a unit of acceleration that is used only in the field of gravimetry, and is 1 centimeter per second squared (cm/s^2).  When measuring the densities of rocks, precision is on the order micro-gals.

Though its cost is significant, a gravitometer is essentially a spring and a mass system.  The spring counteracts the force of gravity pulling on the test mass. Then change in length of the spring may be calibrated to the force required to balance the gravitational pull. 

Wednesday, December 5, 2012

Monitoring Mt. Erebus at Lower Erebus Hut (LEH) Observatory

Lower Erebus Hut (LEH) at the base of Mt. Erebus crater.  Photo: Rebecca Williams

The Lower Erebus Hut (LEH) is the main monitoring station of the Mt. Erebus Volcano Observatory.  This is where we prepare and eat our meals, use our computers with mediocre wireless internet, play bananagrams, and wait out the storms.  The above photo was taken during a weather day with very poor visibility and near whiteout conditions.  The hut seats about 14 max.  

LEH monitoring station.
Infra-red camera image of the lava lake within the crater
Real-time stream of gas concentrations in the crater's plume.

The hut's monitoring station includes a real-time stream of four gas concentrations in the plume rising from the crater, and an infra-red camera image of the lava lake at the base of the crater. The plume results from degassing of the lava lake.

Current research consists of
  1.  continued monitoring of the SO2 flux from the lava lake
  2.  measuring the CO2 emissions from the lava lake and summit
  3. geochronology of the summit and flank lava flows
  4. continued monitoring and interpretation of seismic and seismoacoustic activity volcano through the use of a network of highly-sensitive broad-band seismometers
  5.  establishing a GPS base network to monitor the short- and long-term deformation of the volcano

Tuesday, December 4, 2012

Yeti Goes to Mt. Erebus, Antarctica

Yeti's next adventure is his maiden voyage of science!  This current deployment will be the first ALL SCIENCE campaign to the Poles, which is very exciting for proving his utility for scientific applications as well as for logistic support. 

Yeti will be accompanying an 11-person team of scientists studying Mount Erebus, the highest and southern-most active volcano in the world.  The Mount Erebus Volcano Observatory (MEVO) at the New Mexico Institute of Mining and Technology has been monitoring Mt. Erebus since 1972.  At the head of our team is Phil Kyle, one of the pioneering scientists of Erebus who will be celebrating his 40th season this year. 

Yeti's role in this year's Erebus season will be to collect ground penetrating radar (GPR) images of ice caves that form within the snowpack surrounding the crater.  These caves are formed by fumaroles, which are openings in the volcano that emit steam and various gasses.  Microclimate, heat transfer, extent, and structure are just some of the scientific aspects that are of interest. 

A view of Mt. Erebus from approximately 30 miles south.  A small plume of gas escapes on a nearly windless day.